Liquid-liquid extraction, also called solvent (solvent) extraction, is a selective separation process based on the different solubility of a substance in two insoluble phases (for example, petrol/water). An aqueous phase usually makes up one of the two phases.
Liquid-liquid extraction is particularly suitable for processing large quantities. Flow rates of 100 m³/h and more can be easily archived with reasonable equipment dimensions. Energy consumption is usually negligible since the actual extraction process consumes small amount of energy. However, the subsequent regeneration stage - usually rectification - requires a corresponding expenditure of energy for the recovery of the extractant. For this purpose, the resulting raffinate phase must often be fed to a post-treatment. In general, the regeneration part of an extraction system requires energetic and investment costs many time that of the extraction. Accordingly, selection of the suitable extractant depends not only on the extraction selectivity, but also on the simplest and energetically most economical regeneration option.
The stirred extraction column is like no other apparatus type universally applicable to virtually all liquid-liquid extractions. Only limiting conditions: Minimal density difference of 0.05 kg/m3 and low tendency for emulsion formation.